The invention generally relates to the application of crosswires to a tension focus mask for use in color picture tubes and, more particularly, a method and apparatus of terminating a crosswire to a busbar while maintaining tension on the focus mask.
A color picture tube includes an electron gun for forming and directing three electron beams to a screen of the tube. The screen is located on the inner surface of the faceplate of the tube and is made up of an array of elements of three different color-emitting phosphors. An aperture mask, which may be either a shadow mask or a tension mask, is interposed between the electron gun and the screen to permit each electron beam to strike only the phosphor elements associated with that beam. A shadow mask is a thin sheet of metal, such as steel, that is contoured to somewhat parallel the inner surface of the tube faceplate. A shadow mask may be either domed or tensioned. A type of tension mask, called a tension focus mask, comprises two sets of conductive elements that are perpendicular to each other and separated by an insulator. Two different voltages are applied to the two sets of elements to create quadropole focusing lenses in each of the mask opening, which form a focus mask. The mask openings are defined by the rectangular space between adjacent vertical lines and adjacent horizontal lines. Generally, in a tension focus mask, a vertical set of conductive lines or strands is under tension and a set of horizontal conductive elements sometimes known as crosswires overlies the strands.
In cathode ray tubes containing tension focus masks, the spatial integrity of the strands and crosswires is critical. The crosswires and strands must not move from their respective positions during tube operation or during the fabrication process of the mask assemblies, the matrix or the screening processes. Any such motion of the crosswires could impact the mask strands causing electron beams to misregister or phosphor to matrix misregister. It is therefore desirable that the mask structural elements, especially those used to terminate the crosswires, must be rigid.
The present invention provides an apparatus and method for attaching crosswires to a busbar in a tension focus mask. The apparatus includes a set of elements aligned next to each other and held together by a set of clips. The aligned elements include a busbar support rail that is placed adjacent to a glass busbar. The glass busbar is held against the busbar support rail by busbar clips. A spacer assembly is then added, and a termination strip is put against the spacer assembly. A set of termination strip clips hold the termination strip against the spacer and help to keep all of the elements together. After the elements are aligned and held together by the clips, crosswires from a tension mask are laid across the top of the busbar past the spacer assembly and onto the termination strip. The wires are affixed to the termination strip using a fast-curing adhesive or weld after which a non-structural electrical adhesive is laid across the top of the busbar adhering the crosswires to the top of the busbar. The assembly is then placed in an oven where the non-structural electrical adhesive dries or cures. After the oven cycle, the assembly is removed and allowed to cool after which the crosswires that attach to the termination strip are then removed to provide electrical isolation.